Numerous furnace designs have been utilized to melt high-temperature fusing mineral material into a heat-softened body. One common design for glass utilizes a curved sheet-like metal current-conducting heater element across a melting chamber. See, for example, U.S. Pat. No. 3,264,076. When high amperage electrical current passes through the sheet-like heating element, the heat from the energized element continuously converts input mineral material into molten glass. When the heating arrangement utilizes the melter to supply molten material to a feeder or other apparatus, as shown in U.S. Pat. No. 3,264,076, the heater element is generally oriented across the direction of flow of the molten material towards the outlet to the feeder or other apparatus.
A later melter design, as described in U.S. Pat. No. 3,912,477, provides for increased output or "throughput" by utilizing a bank of spaced parallel "rod-type" heating elements submerged in a body of flowable material in the receptacle. The shapes of the rod-type heating elements described in the above patent application allow greater surface content between the heating elements and the flowable material, thus permitting greater heat transfer and consequently greater throughput. The heating elements in the above patent are rigidly mounted in parallel between two bus bars which supply electrical energy, and the heating elements are made with a refractory core and a thin conductive metal outer coating. This construction allows considerable conservtion of precious high-temperature metals, with a maximum of heat transfer.
One of the heretofore unsolved problems of glass melting furnaces is the problem of expansion of the heating elements caused by the high operating temperatures of the melter. These temperatures may be as high as 1700.degree. C. This problem is particularly acute in the increased throughput "rod-type" heating units. The heating elements are prevented from expanding in the "rod-type" heater because they are rigidly connected to the bus bars, which in turn are rigidly bolted directly to the transformer supplying power to the heating elements. In order to expand, the heating elements must deform. This deformation can lead to premature failure of the heating elements, especially if they are cycled up and down in temperature due to power failures or unit shut-down for cleaning. Premature failure of heating elements results in increased material costs and lower overall production output.